Early Streamer Emission Lightning Protection Systems - Literature Survey and Technical Evaluation Richard J. Van Brunt Thomas L. Nelson Samara L. Firebaugh U.S. DEPARTMENT OF COMMERCE Technology Administration National Institute of Standards and Technology Electronics and Electrical Engineering Laboratory Electricity Division Gaithersburg, MD 20899 NIST QC 100 .U56 N0.5621 1995 / I NISTIR 5621 Early Streamer Emission Lightning Protection Systems - Literature Survey and Technical Evaluation Richard J. Van Brunt Thomas L. Nelson Samara L. Firebaugh U.S. DEPARTMENT OF COMMERCE Technology Administration National Institute of Standards and Technology Electronics and Electrical Engineering Laboratory Electricity Division Gaithersburg, MD 20899 U.S. DEPARTMENT OF COMMERCE Ronald H. Brown, Secretary TECHNOLOGY ADMINISTRATION Mary L. Good, Under Secretary for Technology NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY Arati Prabhakar, Director Early Streamer Emission Lightning Protection Systems Literature Survey and Technical Evaluation Richard J. Van Brunt, Thomas L. Nelson, and Samara L. Firebaugh^ National Institute of Standards and Technology^ Gaithersburg, MD 20899, U.S.A. January 31, 1995 ^NIST summer student, Princeton University, Princeton, NJ ^Electricity Division, Electronics and Electriced Engineering Laboratory, Technology Administration, U.S. Depart- ment of Commerce. Abstract This report has been prepared by the National Institute of Standards and Technology (NIST) at the request of the National Fire Protection Research Foundation (NFPRF) for the purpose of providing information needed to perform a technical evaluation of lightning protection systems based on the early streamer emission (ESE) concept. Included in this document is an annotated bibhography of over 300 publications that were found to be directly or indirectly relevant to ESE technology. Each publication is listed together with an abstract and/or commentary that describes the nature of the work, and each article in the bibhography has been rated according to its perceived importance. Also included is a discussion derived from an examination of the literature cited in the bibhography about the state of knowledge concerning the operation and effectiveness of ESE devices that identifies issues and areas of controversy. The report concludes with recommendations for research that may be needed to resolve remaining issues. 1 ; - 3 !i' Table of Contents Section Page I. INTRODUCTION 1. A. Purpose and Motivation 2. B. Organization of Report 2. C. Definitions 2. II. BIBLIOGRAPHY (Preparation and Organization) 4. III. DISCUSSION 7. A. Characteristics of Lightning 7. B. ESE Air Terminal 10. C. Physical Bases for ESE Air Terminals 12. D. Validation of ESE System Performance 16. 1. Laboratory and small-scale tests 17. 2. Simulations using theoretical models 19. 3. Tests using natural or artificially triggered lightning 20. E. Issues to be Addressed 22. 1. Zone of protection 22. 2. Uncontrollable factors 23. 3. Radiation hazards 24. 4. Damage and maintenance 24. IV. CONCLUSIONS 24. V. RECOMMENDATIONS 27. VI. SUMMARY OF CONCLUSIONS 28. BIBLIOGRAPHY 29. AUTHOR INDEX 181. ii I. INTRODUCTION A. Purpose and Motivation This report has been prepared by the National Institute of Standards and Technology (NIST) at the request of the National Fire Protection Research Foundation (NFPRF) for the primary purpose of providing scientific and technical information needed as a basis for development and evaluation of possible future standards concerned with the use and installation of early streamer emission (ESE) lightning protection systems. The report includes a bibliography of publications relevant to ESE devices and a discussion about the implications of published results on a technical evaluation of these devices. The ESE devices considered in this report are lightning attractors, and in that sense, their purpose is the same as that of an ordinary “lightning rod” sometimes referred to as a “Franklin rod.” The ESE rod differs from the Franklin rod in that it is equipped with a device which supposedly increases the efficiency of lightning attraction and thereby extends the effective range of protection. The term “systems” given in the title is restricted in its meaning to include only the air terminal with its associated instrumentation and controls. The report does not cover issues concerned, for example, with grounding of terminals or with geometrical configurations of multiple-rod arrays. This report examines the physical bases for ESE devices as discussed in the literature. The discussion and conculsions are based entirely on data, observations, and analyses previously published. No laboratory or field testing or theoretical analysis of ESE devices have been conducted by NIST. An attempt has been made to identify existing areas of controversy and gaps in our knowledge about lightning that need to be considered and addressed in assessing ESE devices. B. Organization of Report The report begins with a discussion of how the bibliography is organized and how the items included in the bibliography were selected and rated according to their importance and relevance. The bibliography is annotated in the sense that it includes an abstract and/or commentary about each item listed. The following section of the report includes a discussion of information and issues relevant to ESE technology with appropriate reference to related items listed in the bibliography. The report concludes with recommendations for future work that may be needed to improve the understanding and reliabihty of methods used to test ESE devices and meaningfully compare their performance with that of other lightning protection systems. C. Definitions As an aid to the reader, commonly used technical terms are defined below. It should be cautioned, however, that there is not always universal agreement about the mean- ing of all terms used here and in the bibliography. For example, in discussions of 1 lightning discharge phenomena, there is sometimes confusion in the use of the words “streamer” and “leader” . Some authors use the term leader where others would insist that they should use streamer. There are also cases where different words are used to denote the same phenomenon. For example, a “corona discharge” is sometimes called a “point discharge” or a “partial discharge”. The following definitions reflect the authors’ understanding or interpretation as used in this report and no other claim or recommendation is made about universal acceptance. - 1 . Early streamer emission air terminal Air terminal (lightning rod) equipped with a device that triggers the early initiation of the upward connecting streamer-leader discharge, when compared with a conventional air terminal under the same conditions. 2. Lightning rod- A vertical conducting rod used to attract (or intercept) a lightning strike by producing a local enhancement of the electric field strength in air. This is sometimes called a Franklin rod, conventional air terminal, or lightning conductor. 3. Primary cloud-to-ground (CG) lightning stroke - The initial discharge between a thundercloud and ground that is generally associated with a stepped leader propaga- tion. Four general types of primary strokes need to be distinguished: 1) downward propagating negative stroke from a cloud negatively charged relative to ground (often referred to as normal lightning); 2) downward propagating positive stroke orginating from that part of a thundercloud positively charged relative to ground; 3) upward propagating negative stroke; and 4) upward propagating positive stroke. The primary CG lightning stroke is also referred to sometimes as the intitial stroke or as simply a lighting flash. 4. Stepped leader - Intense spark or plasma channel of finite but variable length in air corresponding to the observed individual steps in a lightning stroke. This is considered to be a relatively high- temperature discharge stage heated by the passage of an electrical current pulse of high magnitude [136,144,162]. 5. Streamer - A narrow, highly-directed, and self-propagating discharge in air. A streamer develops from an electron avalanche when the local space charge becomes of sufficient density to produce an electric-field strength comparable to or greater than the external field, and it is believed to propagate at a high velocity by the mechanism of photoionization in high-field regions produced ahead of the discharge. This is a relatively cold discharge phenomenon which can be the precursor to the formation of a leader step [82,136,176]. 6. Return stroke - This is a discharge that propagates upward from the ground (or lightning rod) in the channel formed by the primary downward stroke. An individ- ual lightning event may exhibit one or more return strokes [159,265]. The return stroke should not be confused with the streamer-leader initiated at a terminal by the advancing primary lightning stroke. 7. Striking distance - The distance covered by the last leader step of a downward prop- agating primary lightning stroke in making contact with a grounded object (lightning 2 rod). This is sometimes called the final jump and it is expected to follow the path of an upward propagating streamer if such a streamer occurs. This distance varies with type and intensity of the lightning stroke. 8. Corona discharge - A localized, cold discharge in air that forms around objects such as sharp conducting points or wires which produce an enhancement in electric-field strength sufficient to allow ionization growth.